Signal-receiving circuits



May s, 192s. 1,669,217

A. H. TAYLOR ET AL S IGNAL RECEIVING CIRCUITS Filed 0011-17, 1925 2 Sheets-Sheet 1 2329.1. f #o w /e 91( w ff 5 4Z Si www4@ gwuanow ZQQ'Z H 72;?01'

Z3/Makel. Wife,

ma. /HM/Q W atto: m11

May 8, 1928. 1,669,217

A. H. TAYLOR ET Al.

SIGNAL RECEIVING CIRCUITS Filed Oct-17, 1925 2 sheets-sheet 2 Het 5.

ation/w11 i Patented May 8, 1928.

UNiTED STATES PATE T OFFICE.

ALBERT H. TAYLOR AND EDWIN L. WHITE, OF WASHINGTON, DISTRICT OF COLUM- BIA., ASSIGNORS T0 WIRED RADIO, INC., 0F NEW YORK, N. Y., A CORPORATION OF DELAWARE.

SIGNAL-RECEIVING- CIRCUITS.

Application filed October 17, 1925. Serial No. 63,158.

Our invention relates broadly to radio receiving circuits and apparatus and more particularly to an arrangement of electron tube circuits and apparatus within a radio receiver by which rugged and durable construction is secured.

One of the objects of our invention is to provide an arrangement of radio receiving apparatus in which shocks, jars and vibration due to shipment or use of the apparatus will not a'ect the operation of the receiver.

Another object of our invention is to provide a system for controlling the operating frequency of the receiving apparatus by means of a piezo electric crystal with means for rendering the apparatus non-microphonic to mechanical vibrations at the same time securing a high degree of sensitivity in the apparatus.

Still another object of our invention is to provide a selective receiving circuit for radio signaling in which the constant frequency characteristics of a piezo electric crystal are utilized for rendering the receiving apparatus selectively responsive to a particular frequency of the incoming signaling' energy with means forcpreventing microphonic noises in the receiving circuits due to vibrations which may be encountered in the use of the apparatus whereby the receiving circuit may be highly sensitive to incoming radio signals.

A further object of our invention is to provide a construction of radio receiving apparatus in which timing is accomplished by angular displacement of metallic plates with respect to fixed inductances and capacities where the plates are made of low resistance material having a natural period of vibration below or above the audible ran e, that is outside of the audible range, or eliminating microphonic noises in the receiving system at the same time that losses due to eddy currents in the metallic plates are reduced to a minimum.

Our invention will be more clearly understood by reference to the following specification and the accompanying drawings, wherein:

Figure l illustrates an arrangement of the receiving circuits of our invention with a piezo electric control for fixing the frequenc of operation of the receiver; Fig. 2 is a iagrammatic view illustrating an arrangement of the circuits in the receiver where microplionic noises are substantially negligible; Fig. 3 is a side elevation showing the construction of the metallic plate tuning devices employed in our receiving circuit arrangement; and Fig. 4 is a crosssectional view through one of the metallic plate tuning devices showing the relation of the angularly movable plate to the inductance.

A great deal of trouble has been experienced in high frequency receivers due to their extreme sensibility to vibration and a large part of this has been traced to vibration of condenser plates which is increasingly annoying as the frequency is increased. These effects are particularly obnoxious in reception on board aircraft and indeed so disastrous in reception aboard heavierthan-air machines, which have more vibration than airships, that designs of receivers heretofore available have been inadequate.

In our design of receiving apparat-us We provide a combination of piezo electric crystal control and non-microphonic or vibrationless construction which has hitherto not been obtained in any receiver to the degree that it is obtained by the present invention; lith reference to the drawings, reference character 1, designates an antenna system which may be balanced against a suitable counterpoise including in circuit the tuning capacity 2 and the inductance 3. The inductance 3 is shunted by means of a fixed condenser 4 having a value proportioned to the inductance 3 for the reception of signals of the desired frequency. The tuning of coil 3 is accomplished by means of a rotatable nietal disk 5 under control of the knob 6. |lihe tuned circuit is shown connected with an electron tube detector 7 with the grid leak and grid condenser 8 in the grid circuit thereof, and with an audio frequency amplifier comprising tubes l() and 12 coupled through transformers 9 and 11 with the output circuit of detector tube 7. 'A suitable jack 14; is arranged in the output circuit of the audio frequency amplifier for the connection of receiving telephones or loud speaker. |The late energy is supplied to the several tubes t rough battery 15 while the lament lighting potential is obtained from battery 16. ln lieu of batteries, suitable generators may be provided driven in any Well-known manner. A special heterodyning or oscillating tube 17 is provided having the frequency thereof controlled by a quartz or other piezo electric crystal 18 in circuit with choke coil 20. In the output circuit of the oscillator 17 we provide a tuning system comprising inductance 2l shunted by fixed condenser 22 with a rotatable metal disk 23 in the field of inductance 21 under control of the adjusting dial 24. A radio frequency by-pass condenser 25 is provided across the battery 15 enabling oscillations to be set up in the circuits of the electron tubes 17. A connection is taken from a oint in the grid circuit of the oscillator tu e 17 through radio frequency choke coil 19 to the negative side of the filament battery to provide a path for the direct grid current to return to the lament. The choke 19 is inserted to prevent frequency voltages developed yby the crystal 18 from passing to ground by the same path instead of being impressed on the grid of the tube 17. Constant high frequency oscillations are impressed upon the incoming oscillations in the detector circuit through inductive coupling between the two coils 21 and 3. We provide a rheostat 28 for controlling the filament temperature for the several tubes.

In Fig. 2 We have shown a self-oscillating receiver wherein an inductance 23 connected in the plate circuit of the tube 7 is inductively coupled with the tuning inductance 3. A radio frequency choke coil 31 is connected in the plate circuit of tube 7 and a Circuit including resistance 29 and capacity 30 is connected between points in the input and output circuits adjacent inductances 3 and 28 for controlling the regenerative operation of the receiving circuit. 7e have illustrated telephones 27 in the output circuit of the receiver. The complete receiving apparatus is flexibly suspended or supported in a shock proof mounting which We haveindicated as enclosed by lines 41 and by spring devices 42. By the provision of the shock proof mounting, microphonic noises in the receiving circuits are substantially reduced. Each of the tuning devices consists of a fixed inductance and a rotatable metal disk mounted therein as shown more clearly in Figs. 3 and 4. The inductance- 3 is mounted Within a frame 32 with the ends of the inductance connected to supporting members 39 and 40 which are arranged to receive a fixed condenser 4 therein. It will be observed that there are no variable tuning condensers in the tuning unit, but that the inductances and the fixed capacity are designed for the particular range of frequencies over which the receiver is. intended to operate. We provide journals 33 and 34 in the frame 32 in which the metallic disk 5 is rotatably mounted on spindles 35 and 36 under control of the rotatable knob 6. The metallic disk 5 has such a thickness that the natural period of the metal is outside of the range of audibility. That is to say7 its natural period may be above the range of audibility or 1t may be below the range of audibility but mechanical vibration of the disk is Such that no microphonic noises are introduced into the receiving circuit under conditions of vibration. Themetallic disk is constructed of low resistance material so that eddy current losses are substantially negligible. ,The construction of disk which we provide is not to be confused with the `thin metal plates which have been heretofore suggested as tuning inductances, for the metallic disk which we provide has the particular feature of having a natural period of vibration outside of the range of audibility and the feature of an extremely low resistance. rfhe metallic disk 5 may be set in any selected angular position by means of a locking clamp 37 engaging both the frame 32 and the rotatable shaft on which the disk is mounted. 'lhe angular disposition of the plate 5 with respect to the inductance 3 is readily determinable by reference of the dial 6 to the index 38.

The receiver of our invention has proven to be very practical in construction and successful in operation. The receiver may be operated for the reception of telephone signals or modulated or interrupted continuous waves. The receiver may also be used 1n continuous wave reception. It is to be understood that any number of stages of amplification may be employed and that radio frequency amplification may precede the detector or additional selective circuits may be provided withthe receiver proper. Additional stages of audio frequency ampliication may be employed and the receiver is not limited to a particular frcquency. In using this receiver in aircraft communication has been successful carried on at 4200 kilocycles. At materially lower frequencies receivers of this type function satisfactorily, but the range of variation from maximum to minimum frequencies is less since the effect of the rotating metal disk is greater for higher frequencies. Our construction of receiver is the only type which has been found to be satisfactory for continuous wave reception aboard aircraft at frequencies in excess of 2000 kilocycles.

While we have described our invention in certain particular embodiments, we desire that it be understood that modifications may be made and that we intend no limitations upon the invent-ion other than those imposed by the scope of the appended claims.

What we claim and desire to secure by Letter Patent of the United States is as follows:

1. A radio receiving system comprising in combination a radio frequency energy collecting circuit, tuning apparatus connected with said radio frequency energy collecting circuit, a plurality of electron tubes connected with said tuning apparatus, said tuning apparatus having means therein for preventing microphonic noises in the receiving system including a variable movable disc member of low resistivity having a natural period of vibration beyond the range of audibility, and a shock proof mounting for said electron tubes for preventing mechanical vibrations from setting up microphonic noises in the receiving system.

2. A radio receiving apparatus comprisin in combination a plurality of electron tu es, a non-microphonic tuning system including a tuner which has no natural period of vibration Withinl the audible range, and a shock proof mounting for said electron tubes for preventing microphonic noises in said apparatus due to shock vibration.

3. A radio receiving system comprising in combination a plurality of electron tubes each having grid, filament and plate electrodes, input andl output circuits interconnecting said electrodes, a tuning system connected with the input circuit of one of said electron tubes, a radio frequency energy collecting system connected with said tuning system and means in said tuning system for preventing microphonic noises in said elec-V tron tube circuits including a variable movable disc member having lovv resistivity and having a natural period outside of the range of audibility, and additional means for mounting said electron tubes for preventing microphonic noises in the circuits thereof due to mechanical vibration.

4. A radio receiving system comprising in combination a radio frequency energy collecting circuit, a tuning circuit connected With said radio frequency energy collecting circuit, a plurality of electron tubes, each having grid, filament and plate electrodes, input and output circuits interconnecting said electrodes, with the input circuit of one of said tubes connected with said tuning circuit, said tuning circuit comprising a fixed inductance and xed capacity shunted thereacross, with a metallic disk of low rcsistivity mounted Within said inductance and arranged to be angularly movable With respect to the axis thereof for adjusting said tuning circuit to resonance with incoming signals, said metallic disk having a natural period beyond the limits of audibility for preventing microphonic noises in said electron tube circuits under conditions of shock vibration, and separate means for protecting said electron tube circuits against shock excitation for further preventing microphonic noises in said receiving apparatus.

5. A radio receiving system comprising in combination a radio frequency energy collecting circuit, a tuning circuit connected therewith, a pluralityof electron tubes each having grid, filament and plate electrodes, input and output circuits interconnecting said electrodes, with the input circuit of one of said electron tubes connected with said tuning circuit, means for flexibly suspending said electron tube circuits for preventing the setting up of microphonic noises therein due to mechanical vibrations, said tuning circuit comprising fixed inductance and capacity with a metallic disk mounted within said inductance, and angularly adjustable therein for tuning said inductance to resonance with the incoming signals, said metallic disk having anatural period beyond the limits of audibility whereby said tuning circuit is protected against the setting up of microphonic noises in said electron tube circuits under conditions of mechanical'vibrations.

6. A radio receiving apparatus comprising a radio frequency energy collecting circuit, a tuning circuit connected with said radio frequency energy collecting circuit, an electron tube detector connected with said tuning circuit and a local generator of high frequency oscillations connected with sald detector, said local generator comprising an electron tube having grid, filament and plate electrodes, input and output circuits interconnecting said electrodes, a piezo electric crystal connected in said input circuit, a separate tuning circuit connected in said output circuit, each of said tuning circuits comprising fixed inductances and capacities with adjustable metallic disks in said inductances, each of said disks having low electrical resistivity and having a natural period beyond audibility for the prevention of microphonic noises in said circuit, said piezo electric crystal operating to prevent a shift in frequency in said receiving circuits under conditions of mechanical vibration.

7. A radio receiving apparatus comprising a radio frequency energy collecting circuit, a tuning circuit connected with said radio frequency energy collecting circuit, an electron tube detector connected with said tuning circuit, a plurality of electron tubes connected with said detector for amplification of incoming signaling energy at audio frequency, and a local generator of high frequency oscillations connected with said detector, said local generator comprising an electron tube having grid, filament and plate electrodes, input and output circuits interconnecting said electrodes,a piezo electric crystal connected in said input circuit, a separate tuning circuit connected in said output circuit, each of said tuning circuits comprising iixed inductances and capacities with adjustable metallic disks in said inductances, each of said disks having low electrical resistivity with a natural period beyond audibility and a shock proof mounting for all of said electron tubes whereby microphonie noises due to vibration of parts of said tuning circuits and vibration of said electron tubes are eliminated,

5 8. A radio receiving system comprising a radio frequency energy collecting circuit, a plurality of electron tubes, a non-microphonic tuning system interconnecting the circuits of said electron tubes and said ra- 10 dio energy collecting circuit, said tuning systern constituting a tuning member having a. natural period of vibration beyond the linfhv its of audibility and a piezo electric crystal frequency controlling element connected with the circuits of said electron tubes for 15 preventing a shift in frequency in said circuits under conditions of shock vibration.

ALBERT H. TAYLOR. EDWIN L. WHITE. 

